The month of February

[xirokx]

Hey,

I created a simple program that tells the user the number of days in a month after they enter the number of the month for the year they are in, however I need to now allow for leap years...I read the vb help files and discovered this code but I do not know how to implent it to my source code:-

Function bIsLeapYear(ByVal inYear As Integer) As Boolean
bIsLeapYear = ((inYear Mod 4 = 0) _
And (inYear Mod 100 <> 0) _
Or (inYear Mod 400 = 0))

Please can someone tell me how to use it in my below source code:-

Option Explicit
Dim Month As Integer
Private Sub cmdMonth_Click()
    Month = InputBox("Please enter a month 1 to 12")
    If Month < "1" Then
        MsgBox "Please enter a number between 1 and 12"
    Else
    If Month > "12" Then
        MsgBox "Please enter a number between 1 and 12"
End If
End If
Select Case Month
    Case 1, 3, 5, 7, 8, 10, 12
        txtDays.Text = 31
    Case 4, 6, 9, 11
        txtDays.Text = 30
    Case 2
        txtDays.Text = "28"
    End Select
End Sub

thanks in advance...

cheers

[akhileshbc]

I had modified your code....:

Option Explicit
Dim intMonth As Integer
Private Sub cmdMonth_Click()
    intMonth = CInt(InputBox("Please enter a month 1 to 12"))
    If intMonth < 1 Or intMonth > 12 Then
        MsgBox "Please enter a number between 1 and 12"
        Exit Sub '~~~> Exit the sub, ie. without executing the rest of the code
    End If
Select Case intMonth
    Case 1, 3, 5, 7, 8, 10, 12
        txtDays.Text = "31"
    Case 4, 6, 9, 11
        txtDays.Text = "30"
    Case 2
      If bIsLeapYear(Year(Date)) = True Then '~~~> You have to pass the year for checking whether it is Leap Year or not. Here, I am passing the current year to the function.
        txtDays.Text = "29"
      Else
        txtDays.Text = "28"
      End If
    End Select
End Sub

Function bIsLeapYear(ByVal inYear As Integer) As Boolean

bIsLeapYear = ((inYear Mod 4 = 0) _
And (inYear Mod 100 <> 0) _
Or (inYear Mod 400 = 0))

End Function

[Ellis Dee]

This is super easy with DateSerial(). It's a one-liner, in fact.

Option Explicit
 
Private Sub cmdMonth_Click()
    Dim lngMonth As Long
 
    lngMonth = Val(InputBox("Please enter a month 1 to 12"))
    Select Case lngMonth
        Case 0 ' User cancelled the InputBox
        Case 1 To 12: txtDays.Text = Day(DateSerial(Year(Now()), lngMonth + 1, 0))
        Case Else: MsgBox "Please enter a number between 1 and 12"
    End Select
End Sub

To be clear, let's take a closer look at the one line of code that does all the calculating:

txtDays.Text = Day(DateSerial(Year(Now()), lngMonth + 1, 0))

DateSerial() takes three arguments: Year, Month, Day

- the Year argument is set to the current year: Year(Now())

- the Month argument is set to the month after the user-specified month by adding 1 to whatever the user specified. Note that if you send 13 as the month argument, DateSerial() will automatically roll over to January of the following year. So this one-liner technique works for all months, even December.

- the Day argument is set to 0. Much like how the month rolls over if you send 13, sending 0 for the Day rolls back to the last day of the previous month. Specifically, it returns "one day before (less than) the first."

So by sending month+1 to roll the month forward and day 0 to roll back one day we always get the last day of the specified month. The Day() function simply returns the DayOfMonth part of the date returned by DateSerial().

[xirokx]

thank you very much

cheers

[akhileshbc]

If your problem is solved, please Mark the Thread as Resolved... (you can find this option in Thread Tools, situated at the top of this page..)

[Hack]

Option Explicit
 
Private Function IsThisALeapYear(ByVal myYear As Integer) As Boolean
     IsThisALeapYear = (29 = Day(DateSerial(myYear, 2, 29)))
End Function
 
Private Sub Command1_Click()
If IsThisALeapYear(2010) = True Then
   MsgBox "Yep"
Else
   MsgBox "Nope"
End If
End Sub

[LaVolpe]

A truly simple way to get nr days in any month, any year. Try it.

NrDays = Day(DateSerial(theYear, theMonth+1, 0))

Edited: Ellis Dee posted this same cheat in #3 above. Oops on me.

[Hack]

But, if you are looking for whether a year is a leap year or not, why are you checking any month other than Februray?

[LaVolpe]

But, if you are looking for whether a year is a leap year or not, why are you checking any month other than Februray?

Per OP's post: "... that tells the user the number of days in a month after they enter the number of the month for the year they are in..."

The leap year issue, IMO, was due to not being able to determine the correct number of days for February. Using Ellis Dee's snippet, no need to know if leap year or not for the purpose of returning the number of days in a month.

[Hack]

Ah..then how about being able to throw in a month number and a year number and have it return how many days there was in that particular month for that particular year.

Option Explicit
 
Private Function DaysInMonth(ByVal iMonth As Integer, ByVal iYear As Integer) As Integer
    Dim dtPlaceHolder As Date
    dtPlaceHolder = DateSerial(iYear, iMonth, 1)
    DaysInMonth = DateAdd("M", 1, dtPlaceHolder) - dtPlaceHolder
End Function
 
Private Sub Command1_Click()
Dim iDays As Integer
iDays = DaysInMonth(2, 2000)
MsgBox iDays
End Sub

Or am I just getting carried away?

[LaVolpe]

Hack, that's what Ellis Dee's snippet does

Day(DateSerial(iYear, iMonth + 1, 0)) replaces any custom function for that purpose.

[Siddharth Rout]

One more version....

Private Sub Command1_Click()
    MsgBox IsLeapYear(2004)
End Sub
 
Function IsLeapYear(SomeValue As Variant) As Boolean
    IsLeapYear = IsDate("2/29/" & SomeValue)
End Function

[xirokx]

sorry guys, I forgot to mention I need to incorporate the use all the following logical operators in my program: AND, OR and NOT which should be added to my initial code so that if the program is run in a leap year the program tells the user there are 29 days in February..

Please therefore try and incorporate the below code and include the NOT operator as well

Function bIsLeapYear(ByVal inYear As Integer) As Boolean

bIsLeapYear = ((inYear Mod 4 = 0) _
And (inYear Mod 100 <> 0) _
Or (inYear Mod 400 = 0))

End Function

Thanks in advance

[akhileshbc]

Have you tried my code...????

[Ellis Dee]

No thanks. I have no interest in providing suboptimal code simply to conform to homework guidelines.

[xirokx]

yes akhilesh I tried your code and it works but I need to use the code below so I make use of AND OR NOT operators in my program

Id be grateful for any assistance?

[anhn]

In North London, that is near to Greenwich, this teacher is an astronomer. He knews only this pseudocode:

if year modulo 400 is 0
       then is_leap_year
else if year modulo 100 is 0
       then not_leap_year
else if year modulo 4 is 0
       then is_leap_year
else
       not_leap_year

and then

if (year modulo 4 is 0) and (year modulo 100 is not 0) or (year modulo 400 is 0)
       then is_leap_year
else
       not_leap_year

[Spoo]

ahn

Seems like an extra set of parentheses would be helpful -- is it
.. ( A and B ) or C, or
.. A and ( B or C ) ?

Spoo

[anhn]

ahn

Seems like an extra set of parentheses would be helpful -- is it
.. ( A and B ) or C, or
.. A and ( B or C ) ?

Spoo

Yes, for sure. But VB has a rule to deal with these operators if there is no parentheses. Try to find out yourself.
The pseudocode above is not VB code, its source is Wiki.
As Ellis, I don't want to go further because I don't want to be an astronomer.

[Spoo]

ahn

Yes, thanks, I'm aware of the relative priority of and and or.
Hence my phrasing "would be helpful" as opposed to "is required".

I wonder if Wiki operators are treated as VB operators.

Spoo